annej - 4:55 pm on Feb 9, 2007 (gmt 0)

Thanks for starting this thread and linking all of the patents.

Here is what I've observed that may be related to this. It's a simplified version and might help people see what we are talking about.

Google has some way of isolating certain phrases that they deem typical of spam sites.

Some of us have pages that have too many of these flag phrases.

But the number of phrases that can cause the penalty depends on other factors.

It appears that these problem phrases do more damage if they are in the page title and possibly the H1 tags.

These phrases are more damaging if they are in inbound or internal linking anchor text.

Strength of inbound links is computed in so the level of problem phrases that hurt a page might be different depending on inbounds.

Google is constantly adjusting this filter so some pages are going in and out of it.

Many of the sites affected by this are well established sites that have all pages but the missing ones ranking quite well. Some of these missing pages had been in the top ten results for years.

It appears to me that pages with few inbound links can be hurt by scrapers as most of the link anchor text will be identical. This give the appearance that a lot of inbound links have the same phrases in the anchor text.

(Let's hear what others have observed)